1. Field of the Invention
The present invention relates to a device and a method for the micro-particulation of filtration residues comprising a mechanical treatment and a heat treatment, in particular of whey proteins in ultra-filtration whey concentrates.
2. The Prior Art
Such a device for the micro-particulation is for example known from the dissertation paper “Thermische Denaturierung und Aggregation von Molkenproteinen in Ultrafiltrationsmolkenkonzentraten—Reaktionskinetik und Partikulieren im Schabewaermetauscher” (“Thermal denaturisation and aggregation of whey proteins in ultra-filtration whey concentrates—reaction kinetics and particulation in the scraped surface heat exchanger”) appearing in the Shaker publishing house under ISBN 3-8265-6233-X in the year 1999.
It is the goal of particulation to create filtration residues, such as e.g. whey protein particles in a size range of a few micrometers. This is generally achieved by a combination of the heat-induced denaturisation and aggregation of the whey proteins, with a mechanical size reduction of the particles. Thus one utilises the superposition of the two procedures of aggregation and particle breakdown, which counteract one another, for the particulation process, in order to obtain a certain size distribution of the particles.
By way of particulation, the filtration residue or specially the whey protein aggregate may be adapted to the specific demands for different types of products. For example, whey proteins in the form of aggregates may be integrated into a cheese matrix in the size range of a few micrometers. The yield is increased, and the texture properties, in particular of low-fat cheeses, are improved. The application in cheese requires particles sizes below 10 μm for example.
The aggregates obtained by particulation, in a certain, as narrow as possible size range, may for example also be used in the manufacture of milk desserts or ice cream in an analogous manner.
With the device for micro-particulation, which is known from the above mentioned dissertation paper, the heat-treatment procedure as well as the procedure for mechanical processing, which means the mechanical size reduction of the particles, are carried out simultaneously in a coupled manner in one and the same apparatus. Thereby, according to the cited state of the art, a scraped surface heat exchanger is applied, in which the whey proteins are introduced from the ultra-filtration whey concentrate. In the scraped surface heat exchanger, the filtration residue on the one hand is heated by the thermal transfer at the transfer surface of the scraped surface heat exchanger. On the other hand, scrapers revolving within the scraped surface heat exchanger produce a shear force, by which means a mechanical size reduction of the particles is achieved.
The disadvantage of this device or with this method for the micro-particulation, is however the fact that the process of the heating, by way of which an aggregate formation is created, is directly coupled to the procedure of the mechanical size reduction. Thus, the heat transfer onto the filtration residue may disadvantageously only be varied by increasing the revolving frequency of the scrapers, which however unavoidably leads to a change in the mechanical size reduction effect. Thus disadvantageously, the counter-running procedures of the aggregation caused by heat treatment, and the size reduction caused by the mechanical shear loading, may not be influenced as independent parameters of the process. This has the disadvantage that it is generally not possible to manufacture particles in a preselected and tight size range. Since furthermore, the size reduction of the particles is only activated with the known method in the scraped surface heat exchanger by way of intensive shear loading, the defined selection of a desired, defined particles size is not possible a priori. Instead, the design and selection of the operating parameters must be effected in an essentially empirical manner. Furthermore, the rotor with the scrapers must be operated at a very high rotational speed for the production of particularly small size ranges of a few micrometers, which are of interest for the mentioned applications. This has the disadvantage that the wear of the scraped surface heat exchanger is particularly large. Furthermore, the operation at a high revolving speed leads to an increased energy consumption.